[gdal-dev] GeomTransform in VRT-file

[Even Rouault]

Le jeudi 04 juillet 2013 18:12:32, Jan Hartmann a écrit :
> I'm struggling with the order of the Geotransform section in a vrt file.
> I would like to rotate an image, and computed the six parameters for the
> affine transformation. I can transform points exactly, using the
> following formula:
> 
> x2 = a.x1 + b.y1 + c
> y2 = d.x1 + e.y1 + f
> 
> Can anyone tell me what the order is in the GeoTransform section of the
> VRT-file?
> 
> <GeoTransform> c a b f d e </GeoTransform>
> 
> results in an image somewhere in the neighbourhood, but mirrored and
> translated. What is the order of the parameters a-f?

That looks correct, assuming that (x1, y1) is expressed as column, row in 
pixels of the image and (x2, y2) is expressed in the output coordinate system.

> 
> Jan
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